Master and Apprentice
by Asymmetric
Summary: When Darkness destroys Destiny Islands, Riku is sent to the Realm of Darkness instead of Hollow Bastion. There, he learns of the keyblade arts from Aqua. But how much will apprenticeship really change him? For Want of A Nail-ish.
1. Chapter 1

A/N: First chapter of my first story. I should introduce myself, eh?

Well, the name's Asymmetric, Tric for short. This is going to be a For Want of A Nail story where, instead of landing in Hollow Bastion, Riku ends up stuck in the Realm of Darkness. It's probably going to be chaptered. So far I have no beta, but that may change.

Reviews – including, you know, _actual_ reviews – would be appreciated.

Oh, and, naturally, I don't own Kingdom Hearts or any of its characters.

* * *

><p>Riku's first thought upon waking was <em>the raft<em>, and that was what alerted him to the nature of the storm outside. It was unlike any other he had seen: dark, oppressively dark, as if there was a hole there where something should be, inky, as if there was a substance that sucked out the light. And it was moving, and it was positioned right over their island. Their island -

He almost went outside too quickly to see Kairi, who was running with him, in the same direction. Her eyes brightened, but she was obviously worried. "We need to get to the island!" she said. "The raft is still there!" And it might be destroyed, she didn't say.

She stopped at the main docks, and then said, quietly: "Maybe we can salvage it. You know. Pick up the pieces. Try again some other time."

But Riku was sure that it could be saved. He said so. "We just have to dig it out. Maybe take it to the secret place."

They nodded and grabbed boats. They couldn't talk at first because of the effort of rowing in the storm – the waves were wilder than either had ever seen. And they were – _alive,_ somehow. Riku dipped his hand in and it came out covered with some inky black substance.

But that only made him afraid, and then angry at his own fear, and he pressed onward as Kairi followed a ways behind.

"Do you see that?" Kairi said. "Over by the paopu tree, there –"

Riku did. There was some sort of vortex. It was like a tornado. Except ...

"I'm going to check it out."

"Riku, you could die! We're only worried about the raft! Right?" But the last word was smaller.

"I'll be fine, Kairi, trust me." But she was still unsure, and he would have seen it on her face if she wasn't behind him.

Soon enough they docked, and then parted. Kairi was to head over to the secret place, to prepare a path for the raft. But she looked back at him. "Riku!"

And then he turned around, and smiled. The smile was so different from Sora's. Where Sora's was bright, and cheerful, and happy, Riku's was confident and determined and focused. Sincere.

_He'll be fine. _Kairi thought.

As she turned around, Riku stepped towards the vortex, and when he crossed the land bridge, the darkness spoke to him.

_A princess is stuck in a gated garden, and she leans next to a fountain and puts her feet into the water, while stroking a giant cat. Her vizier secretly (nonchalantly, hungrily) watches her at the same time-_

_A town square with a guillotine houses not-spirits that move as if they were caught in the wind, while a skeleton in a pinstripe suit corrals them towards a graveyard-_

_A man in a glowing blue suit is caught in an endless battle for survival against a man in a red suit, and he cannot let the other get the upper hand because he knows the battle can be stopped at any time -_

_A blond boy looks down at a girl, who has a red hole through her chest. He looks up, and there is a winged man, and the boy's eyes are filled with hate -_

And then the darkness took the world-visions away, and replaced them with a feeling of possibilities, worlds, vast knowledge.

_The door has opened._

Riku walked forward, but he was afraid, and to his horror, the vortex was feeding on his fear, consuming him.

"I'm not afraid of the darkness!" he said to himself. He said it again louder.

And then his trance stopped. And the pull, towards the vortex, ended. Riku, coldly, clearly, realized that he was about to step in, past something he instinctively knew to be an event horizon, a place-of-no-return. This power was dangerous (_yes_, said a voice that grew smaller and smaller, waiting for a choice).

"Riku!" Sora was running towards him. Riku turned around.

_The door has opened, _said the voice. "The door has opened," Riku said, tasting the words in his mouth.

"What?"

"The door has opened, Sora! We can finally go to other worlds now. Once we step through-" Riku turned around, holding his hands to the sky. His voice became slightly manic. "Once we step through, we might not be able to come back. We may never see our parents again. There's no turning back. But this may be our only chance!"

"But - what _is_ that?" said Sora.

Here Riku stopped, as if that wasn't in the script. "Darkness," he said. But he became doubtful, and the darkness took this chance to battle his innate defenses.

Riku doubled over, in pain. At the same time, heartless swarmed around Sora, and as the heartless became bigger, gained helms and twisted smiles, his friend became overwhelmed.

But Riku was fighting his own, internal battle against a mental attack. It was as if the darkness could see their weaknesses. Neither could stand alone, not against these impossible odds.

_But together?_ said a voice, intrigued.

And then, suddenly, Riku stood atop a circular stained glass depiction of a woman in a long blue dress. The wall of light surrounding the circle trembled once as the darkness tried to gain a hold, then trembled again. A voice appeared in his mind, and Riku knew that it was the key. The key to open worlds.

_We don't have much time_, said the voice. _Why do you want the power of the keyblade?_

_I need to protect my friends_, thought Riku. But he knew that that wasn't the whole answer. He wanted to use the key to see new worlds. He wanted to explore, he wanted to know, because there couldn't be only Destiny Islands. He'd seen people from other worlds, and besides, Destiny Islands was just too small to be all there was.

The circle quaked again, and Riku was sent off balance.

_It would be trivial to protect you, kid, but that comes with risk. Darkness ... you don't want to go that route. And you would. I see it in your heart._

_I've always been protecting him,_ thought Riku.

_He doesn't need it,_ countered the voice. _His heart is just as strong as yours. Whether it is more so remains to be seen, and I don't know where the hell he got it from, but there is potential to use the Keyblade. And his would not be influenced by darkness as yours was. _

_I- _said Riku. _My world was ruined by darkness, _he yelled,_ and Sora is out there, and he might die, and I can't just leave him. I need them both. We were going to explore _together_, you stupid key. Don't take that away from us._

_I'm not your key,_ said the voice, sadly. _I guess you really don't remember. Let me show you._

_What - _Riku said, startled. _Then who -_

And then the darkness broke in.

.

.

"Are you awake?"

Riku woke up with a start, and gasped. Then he saw a figure, a woman, and she was looking down at him.

His eyes narrowed. "Who are you?"

She laughed. "Don't you remember?" She bent down, so he could see her more closely. She had blue hair and eyes.

"I'm sorry. I don't think I ever introduced myself. My name is Aqua."


	2. Chapter 2

While most of the Realm of Darkness would be trying to kill anything with a heart, the Dark Margin was, at the moment, singularly peaceful. A sun that was not a sun held still in the sky, and waves crashed on the shoreline. But sometimes, dark beings would try approaching the sand, so Aqua had made doubly sure to rid the area of as many as possible before Riku woke.

Him appearing from the sky was just about the most surprising thing that had happened in - months? Years? To see a person, a real _person_, with a heart and a body and a mind and everything, and for him to be someone she'd met?

"Now the only thing that can disturb the peace is us," she mused, aloud. She would have to warn him not to get desperate about anything, that usually attracted the darkness.

And then, suddenly, she saw him tossing and turning in the sand, as if he was fighting something. _That makes sense. His heart is fractured._

"Are you awake?" she mused.

At this, Riku violently awoke, gasping as if coming from a nightmare.

His eyes narrowed as he saw her. "Who are you?"

She laughed, softly. "Don't you remember?" She bent down. "I'm sorry, I don't think I ever introduced myself. My name is Aqua."

"You …" Riku put his head in his hands, trying to remember the identity of the blue eyed woman standing next to him.

_Sora, do you like Riku?_

_Of course I like him, he's my best friend!_

_Good. So then, if something happens, and Riku is about to get lost – or say, he starts wandering down a dark path alone – you make sure to stay with him and keep him safe. That's your job, Sora, and I'm counting on __you to do it. Okay?_

His eyes widened. "I met you on our island," he said, slowly. _She had been from another world, just like that man - what was his name?_

But at the moment, he knew that did not have time to reminisce. "Do you know how to get back? Do you know how to travel between worlds? Where are my friends?" By this last question Riku was upright and practically shouting at her; he remembered how he had left Sora and Kairi alone and unprotected, and hated himself for it.

Aqua looked away at the horizon. "I'm sorry. I've been stuck here for a long time. I don't know anything about the Realm of Light as it is now, or how to get there. And I don't know where your friends are."

Riku looked down. "So I'm stuck here too?"

"Yeah." She said. The waves crashed around them as they sat in silence.

Aqua considered Riku. Before he woke up, she had taken advantage of his weakened body and spirit, so she could look at his heart. He obviously could use a keyblade, but - something was blocking it. There was this untapped power inside of him, bottled up. And from that, darkness grew. His light was in a constant battle to contain it, and it always - barely - came out ahead.

_That's what happens when you keep part of yourself bottled up, but why ... ?_

Normally the amount of darkness in a heart didn't matter if someone had the potential to use the keyblade; usually it was strength of heart (resolve, willpower, ability to persevere against impossible odds, hope) that made someone able or unable to use it. But Riku's heart was certainly strong enough. He practically reeked with focus.

_Why is he fighting his darkness? And why do I get the feeling that bad things would happen if he didn't?_

Because it was possible that that _wasn't_ his darkness. And if it was foreign ...

Well. Then he would really be in trouble; Riku's heart had become compartmentalized, and it would be frighteningly easy for him to be possessed.

Aqua's thoughts came back to her as Riku began to kick the sand into the air. "So much for seeing other worlds." he grumbled, breaking the silence.

"How did you get here?" Aqua asked.

"There was a storm outside, and it was going to tear apart a raft we built. The storm - I'd heard about darkness as a kid, but I always thought it was just a metaphor. And then it broke into my heart, but something's holding it back."

Aqua sighed, inwardly. Helping him would be tricky. One wrong move and his heart might be ripped out.

"Is it your light? That's holding the darkness back?" said Aqua.

"I don't know," said Riku. "All I know about this stuff comes from the stories our parents used to tell us as kids." And instinctual knowledge that he doesn't know how he knows, and the knowledge the darkness gave him of other worlds, and that voice that talked to him in his heart - but Riku wasn't going to tell Aqua that. He was still ashamed of it.

Then, suddenly, heartless appeared behind them.

Riku cursed. He didn't have a weapon - even his toy sword was lost. But before he could react further, fire and lightning came out of Aqua's hands, dancing around her until all of the heartless vanished.

"You would think," she said, when she was done, "that they would eventually learn." She sighed, then sat back down again.

"How about you? How did you get here?" asked Riku, once Aqua was properly seated.

"I sacrificed my keyblade and armor a long time ago, to protect my friends. Oh, yeah," she said, as Riku suddenly became very interested, "I used to be a keyblade master. Riku … on the day I met you, I saw that he had - that you had been given the ability to use a keyblade."

"Well, so much for that," said Riku, bitterly. "I tried to use it on my island, and it didn't work."

And here was the proverbial moment of truth. Aqua _could_ teach him, and teaching him might be the only way in the foreseeable future for her to get back, but she had no idea how much it would cost him.

She thought of Terra, trapped by Xehanort, and Ven, whose body was in Castle Oblivion.

_I need to help them._

Maybe it was the darkness that led her to this thought. At this point, she didn't care. For all she knew, Riku was a gift from the light; she couldn't escape the feeling that they could make a door, if they tried, and what a boon that would be. But why would the light send an innocent boy here, away from his friends, after the darkness destroyed his world? Into the Realm of Darkness, the most dangerous place she could think of?

_I need to help him, too._

Finally, she spoke. "I could teach you how. I had - _have_ - a friend with the same problem."

"What problem?" Riku said. "I'm not weak."

Aqua smiled inwardly. He really was just like Terra. "I'm not saying you are. But, in order to find your keyblade, you have to know how to seek out the light in your heart, and draw out its power. And I can help you with that."

"Wait. My keyblade? Isn't there only one?"

"No, actually. Normally keyblades are passed along. That's why there are so few - too many people died before they could pass them on in the Keyblade War. You've heard of that, right?"

"Yeah. In stories. People wanted to keep the light for themselves, right?"

"And thus, darkness was born. You've got it." Aqua paused. "So? Do you want my help?"

Riku considered the offer. "Why are you helping me do this?"

"I've been stuck here for so long that it's nice to see someone else who's not a ... " What did Yen Sid call those things again? They've gone through so many names.

"Heartless." Riku immediately supplied. _Wait, what?_ he thought._ How do I know that? _

"A Heartless, then." said Aqua. "And, there's another reason: we can't go back without a keyblade. But maybe, once you can summon it, you can make a path."

Riku took only a second to decide. He needed any help he could get to be stronger. "I accept," he said, resolved. "Teach me how to use a keyblade."


	3. Chapter 3

Aqua and Riku sat next to each other on a rock set deep into the sand. "Before I tell you where to go looking for your light," Aqua said, "you need to know what light is. And darkness, too. So let's begin."

"There are two forces of power in all the worlds: Light," and suddenly a ball of the brightest light appeared in her right hand, "and darkness." She dispelled the light, gesturing at the darkness of their surroundings.

"Darkness is normally considered to be all the negative emotions: rage, hate, jealousy, greed. It's actually more than that. A better word would be _obsession_, because even though it isn't always a negative emotion, it is the true source of the darkness in peoples' hearts. The obsession for revenge, the obsession to pursue wealth, or the obsession for knowledge - all these can lead down a dark path. Oftentimes the use of darkness is because the user is angry or jealous or greedy, which is why it's difficult to distinguish the two. But users of darkness always have some goal - some reason they need the power. And to them, their goal is the most important thing in the world.

"Darkness makes people feel powerful, but it consumes them if they tap into it too much. The reason for that is complicated - sometimes they feel like they have exhausted all their other options. Sometimes, after terrible misfortune, they feel as though they have nothing left to lose. In the end, when they give in entirely, well. That's what creates those things.

"Heartless is a misnomer, really. They're all heart, since they have to leave the body and spirit behind. What they really are are corrupted hearts. The darkness gives them form, and continues to make them feel powerful, while they succumb to their instincts, only bowing to those who obviously have more power than they. It's a sad sort of existence."

Riku listened to her, enraptured. It wasn't immediately obvious that Aqua was a keyblade master, but once she began to talk about the Light and Darkness, it was impossible to mistake.

"Now," she continued, "I said that obsession _can_ lead down a dark path, and that's true, because it doesn't always. People can be fettered - knowing what they will and will not do to pursue their goals. And through that, by knowing exactly where to draw the line, people can draw upon darkness. But you know what they say about slippery slopes. No?" she said, as Riku shook his head. "Well, the idea is that once they get a taste of power, their boundaries start to … slip. And it's all downhill from there.

"Since anyone who uses darkness has a chance to succumb to it, it's safer not to use it at all.

"By contrast, light is the complete and unselfish desire to protect. Pure light grants a warm sensation of safety for that reason. Of course, this isn't entirely positive, either. But those who use light tend to be decent people, so I know where I'm placing my bets." she chucked, then grew deadly serious. "When I say the darkness is dangerous, I mean it. There's nothing down there" she pointed to the hills and valleys of the rest of the Realm of Darkness "except monsters who can and will try to take your heart."

"Do you understand all this?" she asked Riku, who seemed to be concentrating very hard on something. After a while, he spoke up. "Yeah. I think I've got it. Darkness isn't evil and light isn't good. That's why there needs to be a balance, right?"

"Well, sort of. Darkness - darkness _corrupts_. It seeks to perpetuate itself. So it falls to the remaining keyblade masters to protect the light." Aqua put a finger on her chin, thinking. "Let's start with magic."

Suddenly, Aqua thrust out her hand and hit Riku in the chest with a minor fire spell. He was sent flying backwards, into the sand. Then his chest glowed red, but after a couple of seconds, the glow vanished.

"What the hell?"

"Quick, reach for it!" yelled Aqua, suddenly further away.

But the glow had vanished! How could he -

But then he concentrated, and, in doing so, he could feel a warm glow throughout his body.

_Oh_, he thought, in realization. _It's still there._

As he concentrated more on that feeling, his arm began to itch, as if the fire was trying to get out somehow. Then the itch became unbearable, and he knew he had to release it -

"_Fire!_"

- and he was definitely _not_ expecting that amount of recoil, or the draining feeling that accompanied it. But the spell had worked, and that was enough.

_I'm doing magic! Just wait till I tell Sora._

He looked at his arm, grinning. Then he looked at Aqua, who was behind a rock, protected by a force field that she had conjured.

"Well," said Aqua, panting. "Since the spell didn't blow up in your face, I'm going to consider that a success." She poked him in the forehead. "Now you can defend yourself in a pinch. Please know that I would never have given you any spell if we were in a safer place. As it is, you are to avoid_ if at all possible"_ - she poked him four more times for emphasis - "using that on the heartless - you can only shoot so many times before your magical energy runs out."

"Cut that out," said Riku, slapping her hand away. But he was still smiling, if only slightly, from his little victory.

"Okay, then. Now onto another spell." Aqua raised one hand over her head, and conjured a force field around herself. "Hit me with a fire spell."

"What if it goes through?" said Riku, wary.

"It won't. Just do it."

Again, Riku pulled at that warmth inside him, and sent it through his arm.

"_Fire!_"

The ball of energy hit Aqua's barrier, then shot back towards him.

Riku cursed, then rolled out of the way just in time for the spell to hit the spot where he had just been.

"Are you ... trying ... to kill me?" he yelled at Aqua, winded.

"No. Just try focusing on sending the spell back to me."

And that began their odd game of one-sided magical catch. It took what seemed like hours for Riku to actually be able to stop the spell ("_Reflect!_"), let alone send it back. Then, he was told to work on adjusting his aim, which involved yet more practice. When he could finally volley the fire spell back to Aqua, she sent it towards the sea. "I think we need a break," she said.

Riku nodded, and collapsed on a rock. Aqua walked over to join him.

"So," he said, looking at his hand, "what does this all have to do with finding my light?"

"You do need to be able to protect yourself," said Aqua, "and those aren't the only one you're going to learn."

What she didn't say was that it might - eventually - help him see where he needed to look when he drew upon his light, but she was still afraid for him to try. In truth, she needed to keep him occupied while he dealt with his darkness, and she had absolutely no idea how long that would take. But Aqua had been waiting for over ten years - she could afford to wait a little longer if it ensured their safety.

_Soon, we'll be able to leave. But I need to make sure that we survive it, first._


End file.
